Riannon

From Witcher Wiki

Riannon was the daughter of Lara Dorren and Cragen of Lod, and thus the great-great-great-grandmother of Ciri.
Cerro, the queen of Redania at the time, adopted her soon after her birth and named her.
At the age of seventeen, Riannon married Goidemar, the king of Temeria.

During the Falka rebellion, the pregnant Riannon was imprisoned, and gave birth to twins, Fiona and Amavet, and went mad. That didn't stop Falka from giving her own newborn daughter to the prisoner to nurse, though.
When the rebellion was quelled, Riannon returned to her husband, with three children in tow.
Due to her insanity, Riannon was unable to tell which one of the children wasn't hers.

She died at the age of 38.